Add regression test for issue #64153.

Author: michaelwoerister

src/test/run-make-fulldeps/issue-64153/Makefile

@@ -0,0 +1,20 @@
+-include ../tools.mk
+
+# Staticlibs don't include Rust object files from upstream crates if the same
+# code was already pulled into the lib via LTO. However, the bug described in
+# https://github.com/rust-lang/rust/issues/64153 lead to this exclusion not
+# working properly if the upstream crate was compiled with an explicit filename
+# (via `-o`).
+#
+# This test makes sure that functions defined in the upstream crates do not
+# appear twice in the final staticlib when listing all the symbols from it.
+
+all:
+	$(RUSTC) --crate-type rlib upstream.rs -o $(TMPDIR)/libupstream.rlib -Ccodegen-units=1
+	$(RUSTC) --crate-type staticlib downstream.rs -Clto -Ccodegen-units=1 -o $(TMPDIR)/libdownstream.a
+	# Dump all the symbols from the staticlib into `syms`
+	nm $(TMPDIR)/libdownstream.a > $(TMPDIR)/syms
+	# Count the global instances of `issue64153_test_function`. There'll be 2
+	# if the `upstream` object file got erronously included twice.
+	grep -c -e "[[:space:]]T[[:space:]]issue64153_test_function" $(TMPDIR)/syms > $(TMPDIR)/count
+	[ "$$(cat $(TMPDIR)/count)" -eq "1" ]

src/test/run-make-fulldeps/issue-64153/downstream.rs

@@ -0,0 +1,6 @@
+extern crate upstream;
+
+#[no_mangle]
+pub extern "C" fn foo() {
+    print!("1 + 1 = {}", upstream::issue64153_test_function(1));
+}

src/test/run-make-fulldeps/issue-64153/upstream.rs

@@ -0,0 +1,6 @@
+// Make this function extern "C", public, and no-mangle, so that it gets
+// exported from the downstream staticlib.
+#[no_mangle]
+pub extern "C" fn issue64153_test_function(x: u32) -> u32 {
+    x + 1
+}